The structure of the YMR head, which is well known and applied, is indicated in FIG. 7. The upper Yoke (1 and 5) is usually made of about 0.5-1.0 .mu.m permalloy film, and structures the magnetic flux introduction leading the signal magnetic field generated in the magnetic recording medium to the MR element (2). Ferromagnetic film (3) has large magnetic coercive force and high electric conductivity. The ferromagnetic film 3 is made of Co-P, Ni-Co, and Ni-Co-P and so on, and has a film thickness of 1000-2000 .ANG..
The lead conductor (4) is made of Al-Cu film or another conductive metal film, with a film thickness of 1OOO-2000 .ANG.. Located below the above mentioned MR element (2) is the conductor (6), made of Al-Cu film or another conductive metal film, which is set to apply a bias magnetic field to the MR element. The lower yoke (7) is made of a substrate with high magnetic permeability. For this magnetic substrate, polycrystal Ni-Zn ferrite substrate, single crystal or polycrystal Mn-Zn ferrite substrate is normally used. The head gap (10) is set at about 0.2-0.3 .mu.m, since the minimum recording wave length actually used is about 0.5 .mu.m. Also at a location close to the head gap is located the magnetic recording medium (9), as illustrated in FIG. 8. Between the magnetic recording medium (9) and the head gap (10), a spacing (8) is formed.
In a YMR head of this structure, the direction of the easy axis of magnetization of MR the element (2) is set along the longitudinal direction of the MR element (2) when the MR element is fabricated. The detection of the signal magnetic field generated from the above mentioned magnetic recording medium (9) is performed by a flowing sense current along the longitudinal direction of the MR element (2), sensing voltage changes which occur at both ends of such an MR element. The MR element (2) operating point is shifted to a point providing excellent linearity by applying a desirable bias magnetic field, generated by a flowing current through the conductor (6) to the MR element. Also, by ferromagnetic exchange coupling between the above ferromagnetic film (3) and the MR element (2), a weak magnetic field is applied in the longitudinal direction of the MR element (2). This weak magnetic field puts the MR element (2) into a single magnetic domain condition, and suppresses Barkhausen noise from occurring by preventing the MR element (2) magnetization from discontinuously changing.
In conventional YMR heads, generally all directions of the easy axis of magnetization in the entire area of MR element (2) are not in the same direction. This is because the angle dispersion of the easy axis of magnetization tends to occur when the MR element (2) is made, or when the above mentioned head gap (10) and upper yoke (1 and 5) are formed. This causes the easy axis dispersion in each area of the MR element (2). It is difficult to prevent this dispersion. Suppose that the direction of the easy axis of magnetization of points a, b, c, d, and e of MR element, (2) are in the arrowhead (.fwdarw.) directions, as illustrated in FIG. 9. The weak magnetic field direction, the longitudinal direction of the MR element (2) caused by ferromagnetic film (3), is graphically illustrated to be from left to right, that is, in the direction of arrows. Then the magnetization curve of the MR element (2) strip width direction in the individual a, b, c, d, and e points are illustrated by (a)-(e) of FIG. 10 respectively.
In the .DELTA.R/R curve corresponding to such an MR element (2) reproducing output, discontinuous jumps occur in parts of the .DELTA.R/R curve by responding to magnetic transition in the MR element (2), as illustrated in FIG. 2(f)which generates Barkhausen noise. At the same time, if the above mentioned direction of the easy axis of magnetization is set along the longitudinal direction when the MR element (2) is made, the distribution of the direction of the easy axis of magnetization in the MR element (2) becomes distributed in both positive and negative directions of the longitudinal direction.
Consequently, on the axis of the abscissa for the .DELTA.R/R curve, that is, on both negative and positive sides of the magnetic field Ha, for the signal magnetic field, discontinuous jumps occur. Therefore when the MR element (2) operating point is shifted to a point having excellent linearity by a bias magnetic field, a problem results where Barkhausen noise occurs in whatever positive or negative magnetic field direction that an operating point is shifted.